Blob support for IDB [Chromium]

content/browser/indexed_db/indexed_db_active_blob_registry.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/task_runner.h"
+#include "content/browser/indexed_db/indexed_db_active_blob_registry.h"
+#include "content/browser/indexed_db/indexed_db_backing_store.h"
+#include "content/browser/indexed_db/indexed_db_leveldb_coding.h"
+
+namespace content {
+
+IndexedDBActiveBlobRegistry::IndexedDBActiveBlobRegistry(
+      IndexedDBBackingStore* backing_store)
+  : backing_store_(backing_store) {
+}
+
+IndexedDBActiveBlobRegistry::~IndexedDBActiveBlobRegistry() {
+}
+
+void IndexedDBActiveBlobRegistry::MarkUsed(int64 database_id, int64 blob_key) {
+  fprintf(stderr, "ERICU: MarkUsed(%ld, %ld).\n", database_id, blob_key);
+  DCHECK(backing_store_->task_runner()->RunsTasksOnCurrentThread());
+  DCHECK(KeyPrefix::IsValidDatabaseId(database_id));
+  DCHECK(DatabaseMetaDataKey::IsValidBlobKey(blob_key));
+  SingleDBMap& single_db_map = use_counts_[database_id];
+  SingleDBMap::iterator iter = single_db_map.find(blob_key);
+  if (iter == single_db_map.end()) {
+    single_db_map[blob_key] = false;

[jsbell, 2013/09/13 00:12:21]

Call me an optimist, but could we swap the sense of the map so true = alive,
false = dead? (Otherwise this is more of a DeadBlobRegistry)

[ericu, 2013/11/20 23:05:39]

Well, it's a little awkward the other way, too.  Right now the flag means "is it
marked as deleted", for in-use blobs.  If I swapped it, I'd really have to call
that flag "is not deleted yet", which just adds an extra logical inversion.

Databases and blobs that are not in active use aren't tracked by this map/class,
so it really is an active blob registry, as well as a deleted blob registry.

+    backing_store_->AddRef();
+  } else {
+    DCHECK(!iter->second); // You can't add a reference once it's been deleted.
+  }
+}
+
+void IndexedDBActiveBlobRegistry::MarkUnused(

[jsbell, 2013/09/13 00:12:21]

"Unused" in backing store means it has zero references and can be dropped. Here,
"Unused" means decrement the reference count. Maybe tweak the name here?

[ericu, 2013/11/20 23:05:39]

Done.

+    int64 database_id, int64 blob_key) {
+  fprintf(stderr, "ERICU: MarkUnused(%ld, %ld).\n", database_id, blob_key);
+  DCHECK(backing_store_->task_runner()->RunsTasksOnCurrentThread());
+  DCHECK(KeyPrefix::IsValidDatabaseId(database_id));
+  DCHECK(DatabaseMetaDataKey::IsValidBlobKey(blob_key));
+  AllDBsMap::iterator all_dbs_iter = use_counts_.find(database_id);

[jsbell, 2013/09/13 00:12:21]

I'd tweak this variable name based on what it has rather than where it came
from.

[ericu, 2013/11/20 23:05:39]

Ug.  I had a lot of trouble with those names--didn't want to confuse
iterator-over-databases with iterator-over-records-in-a-single-database.  I've
renamed it [and the one below]; let me know if you think that's better.

+  if (all_dbs_iter == use_counts_.end()) {
+    NOTREACHED();
+    return;
+  }
+  SingleDBMap& single_db = all_dbs_iter->second;
+  SingleDBMap::iterator single_db_iter = single_db.find(blob_key);

[jsbell, 2013/09/13 00:12:21]

Ditto - name the iterator for what it holds, not where it came from.

[ericu, 2013/11/20 23:05:39]

Done.

+  if (single_db_iter == single_db.end()) {
+    NOTREACHED();
+    return;
+  }
+  bool delete_in_backend = false;
+  DeletedDBSet::iterator db_to_delete = deleted_dbs_.find(database_id);
+  bool db_marked_for_deletion = db_to_delete != deleted_dbs_.end();
+  // Don't bother deleting the file if we're going to delete its whole
+  // database directory soon.
+  delete_in_backend = single_db_iter->second && !db_marked_for_deletion;
+  fprintf(stderr, "ERICU: MarkUnused delete_in_backend, db_m_f_d are %d, %d.\n",
+      delete_in_backend, db_marked_for_deletion);
+  single_db.erase(single_db_iter);
+  if (!single_db.size()) {

[jsbell, 2013/09/13 00:12:21]

nit: use empty()

[ericu, 2013/11/20 23:05:39]

Done.

+    fprintf(stderr, "ERICU: single_db is empty now.\n");
+    use_counts_.erase(all_dbs_iter);
+    if (db_marked_for_deletion) {
+      fprintf(stderr, "ERICU: db_marked_for_deletion.\n");
+      delete_in_backend = true;
+      blob_key = DatabaseMetaDataKey::kAllBlobsKey;
+      deleted_dbs_.erase(db_to_delete);
+    }
+  }
+  if (delete_in_backend)
+    backing_store_->ReportBlobUnused(database_id, blob_key);
+  backing_store_->Release();
+}
+
+bool IndexedDBActiveBlobRegistry::MarkDeletedCheckIfUsed(
+  int64 database_id, int64 blob_key) {
+  fprintf(stderr, "ERICU: MarkDeletedCheckIfUsed(%ld, %ld).\n",
+      database_id, blob_key);
+  DCHECK(backing_store_->task_runner()->RunsTasksOnCurrentThread());
+  DCHECK(KeyPrefix::IsValidDatabaseId(database_id));
+  AllDBsMap::iterator all_dbs_iter = use_counts_.find(database_id);
+  if (all_dbs_iter == use_counts_.end())
+    return false;
+
+  if (blob_key == DatabaseMetaDataKey::kAllBlobsKey) {
+    deleted_dbs_.insert(database_id);
+    fprintf(stderr, "ERICU: MarkDeletedCheckIfUsed returning early true.\n");
+    return true;
+  }
+
+  SingleDBMap& single_db = all_dbs_iter->second;
+  SingleDBMap::iterator iter = single_db.find(blob_key);
+  if (iter == single_db.end())
+    return false;
+
+  fprintf(stderr, "ERICU: MarkDeletedCheckIfUsed returning true.\n");
+  iter->second = true;
+  return true;
+}
+
+void IndexedDBActiveBlobRegistry::MarkUnusedThreadSafe(
+    int64 database_id, int64 blob_key, const base::FilePath& unused) {
+  backing_store_->task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &IndexedDBActiveBlobRegistry::MarkUnused, base::Unretained(this),
+          database_id, blob_key));
+}
+
+webkit_blob::ShareableFileReference::FinalReleaseCallback
+IndexedDBActiveBlobRegistry::GetReleaseCallback(
+    int64 database_id, int64 blob_key) {
+  return base::Bind(
+      &IndexedDBActiveBlobRegistry::MarkUnusedThreadSafe,
+      base::Unretained(this), database_id, blob_key);
+}
+
+base::Closure IndexedDBActiveBlobRegistry::GetMarkUsedCallback(
+    int64 database_id, int64 blob_key) {
+  return base::Bind(
+      &IndexedDBActiveBlobRegistry::MarkUsed,
+      base::Unretained(this), database_id, blob_key);
+}
+
+} // namespace content